This way, I would know whether my average speed on the flat is increasing, and if I'm getting better on climbs.
Probably the best way to do find out if you're improving is is to find flat out and back route, and do a full out time trial every little while. Ideally it should take at least 20 minutes, and it will not be fun...
My average heart rate was 172 bpm (I'm a 32 year old male, with resting heart rate of 55 bpm. I'm about 4 kg, or 8 lbs fatter than my supposed ideal weight).
Heart rate zones are usually based of lactic threshold heart rate, or max heart rate, and vary a lot from person to person. I think the way you test your lactic threshold heart rate is basically to do a 30 minute time trial, and use the average heart rate for your last 20 minutes.
Don't think so much.
I could not disagree more with this statement.